Thermistor temperature calculation formula program

One 、 Thermistor formula

NTC Thermistor temperature calculation formula ：Rt = R *EXP(B*(1/T1-1/T2))

among ,T1 and T2 refer to K degree , Kelvin temperature .

Rt It's the thermistor in the T1 Resistance at temperature .

R It's the thermistor in the T2 Nominal resistance at room temperature .100K Thermistor 25℃ The value of is 100K（ namely R=100K）.T2=(273.15+25)

EXP yes e Of n Power

B Value is an important parameter of thermistor

The temperature can be obtained by conversion T1 And resistance Rt The relationship between T1=1/（ln（Rt/R）/B+1/T2）

The corresponding Celsius temperature t=T1-273.15, meanwhile +0.5 Error correction .

Two 、 Hardware connection

SCM is 3.3V Power supply , Thermistor and 100K Resistance connection .

The thermistor parameters are 100K,B The value is 3950

3、 ... and 、 Program

Here is the procedure （stm32）, Tested 4 Road temperature

Because you need to use mathematical functions, you need to add header files #include "math.h"

Then write the formula （ Voltage conversion 、 Resistance conversion 、 Temperature conversion ）

Four 、ln、log、lg explain

Formulas in mathematics and c There are small differences in language .

1、 In Mathematics

log It's a logarithmic sign , Photo number and base number on the right （ Above is the real number , Here is the base ）

lg In order to 10 Base number （ example lg100=2）（lg Is the common logarithm ）

ln In order to e Base number （lne2=2）（ln For natural logarithm e=2.7182818284590452353602874713527...）

2、c In language

c There are only two functions in the language log and log10

among

function log(x) It's expressed in e The natural logarithm of the base , namely ln(x)

function log10(x) With 10 Log base , namely lg(x)

The logarithm with other numbers as the base is expressed by the formula of changing the base

Function as follows ：

double logab(double a,double b)
{
return log(b)/log(a);
}